This application is a 371 of PCT/EP97/03899 filed Jul. 21, 1997.
The present invention relates to the use of (meth)acrylic acid copolymers for increasing mucosal permeability.
Epithelial tissue forms an important permeation barrier to the paracellular transport of hydrophilic active substances, especially those of high molecular weights. What are called xe2x80x9ctight junctionsxe2x80x9d (intercellular junctions between adjacent epithelial cells where the plasma membranes are in direct contact) ensure that the internal environment of an organ is sealed off from the external one. The passive paracellular permeability of these epithelial cells is determined by the tightness of the intercellular contact points. Widening of the xe2x80x9ctight junctionsxe2x80x9d leads to improved absorption and thus to a higher bioavailability of active substances.
Hence there has been no lack of attempts in the past to develop methods for opening intercellular contact points. It has emerged from this that the use of both surface-active ingredients and of Ca2+-chelating substances were promising approaches.
However, J. Controlled Rel., 29 (1994) 253 states that on use of surface-active substances there is a risk of cytolysis and, associated with this, toxic side effects.
Numerous publications, inter alia in J. Controlled Rel., 36 (1995) 25; Chem. Pharm. Bull. 33 (1985) 4600; The Journal of Cell Biology, 87 (1980) 736 and Int. J. Pharm., 90 (1993) 229 describe the effect of EDTA or EGTA on the permeability of various cell systems, eg. of caco-2 cells. According to these, the presence of Ca2+-chelating substances may lead to rapid, but frequently irreversible, opening of the tight junctions. In addition, in the case of EDTA, relatively high concentrations are required for an effect to be observed (reduction in transepithelial resistance) at neutral pH. In addition, complexing agents with a molecular weight xe2x89xa620 kDa are associated with the risk that they undergo systematic absorption and thus may result in unwanted toxic side effects.
It was possible to show, in J. Controlled Rel., 29 (1994) 329, that nonabsorbable high molecular weight compounds based on crosslinked polyacrylates such as polycarbophil (Noveon(copyright) AA1, B. F. Goodrich) are likewise able to open tight junctions. There are technical disadvantages on use thereof because of their extremely high molecular weight ( greater than 1000 kDa) and their high viscosity even at low concentrations (xe2x89xa70.5% by weight).
It is furthermore known that polymers with bioadhesive properties are able to improve the bioavailability of active substances. Thus, for example, EP-A-587 047 describes the use of copolymers of (meth)acrylates with various unsaturated carboxylic acids for gestagen-based pharmaceutical compositions.
EP-B-410 422 discloses the possibility of increasing the bioavailability of active substances of low solubility by them being after formulation, owing to the effect of (meth)acrylic acid/(meth)acrylate copolymers, amorphous and thus more soluble.
It is an object of the present invention to find polymers which reversibly increase the permeability of epithelial cells without at the same time having the abovementioned technical disadvantages on use or causing toxicity problems.
We have found that this object is achieved by using (meth)acrylic acid copolymers to increase mucosal permeability and thus enhance the permeation of active substances.
The copolymers according to the invention comprise as monomers acrylic acid or methacrylic acid, which can be employed in the form of their free acid, their salts and/or their anhydrides.
If the monomers are used in the form of their salts for polymerization, the alkaline earth metal, alkali metal or ammonium salts or the salts of organic amines are preferred, and the alkali metal or ammonium salts are particularly preferred.
Further comonomers present are (meth)acrylic acid esters and/or other monomers capable of free-radical polymerization. (Meth)acrylic acid esters of saturated, linear or branched C1-C40-alcohols are used. For example methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, tert-butyl, n-hexyl, n-octyl, i-nonyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-hepta-decyl, n-octadecyl, n-nonadecyl, n-eicosyl, n-docosyl, n-tetra-cosyl, 2-ethylhexyl, i-bornyl acrylate or cyclohexyl acrylate or the corresponding methacrylates. C1-C6- and/or C6-C30-alkyl acrylates or methacrylates are preferably employed. Particularly preferred representatives of the group with a C1-C6 chain are methyl methacrylate, ethyl acrylate and butyl acrylate, and C8-C22-alkyl (meth)acrylates from the group with a C6-C30 chain.
It is also possible to use styrene and/or vinyl esters of saturated C1-C30 carboxylic acids as monomer units. Preferred examples thereof are vinyl acetate and/or vinyl propionate.
The (meth)acrylic acid: comonomer molar ratio in the copolymer according to the invention can be varied widely. It is, for example, in the range from 99:1 to 1:99, preferably from 70:30 to 30:70.
The copolymers are normally administered in the form of pharmaceutical compositions together with the active substance. Suitable pharmaceutical forms are tablets, extrudates, granules, pellets, powders, capsules, suppositories, ointments, suspensions or emulsions, it being possible for administration to take place, depending on the application, orally, sublingually, buccally, rectally, through the lungs, nasally or through the mucosa of the eye. Preferred pharmaceutical forms are a) matrix tablets, b) layered tablets and c) film-coated tablets. Matrix tablets in particular, in which the polymer according to the invention and the active substance are intermittently mixed and then compressed together, represent a form with a high activity potential. The content of copolymer to be used according to the invention in these pharmaceutical forms is generally more than 50%, in particular from 60 to 99%, preferably from 75 to 99%, of the total weight of the form. However, it is also possible firstly to treat the mucosa, e.g. of the intestine, throat or eye, with the permeability-increasing copolymer and then to administer the pharmaceutical active substance.
The abovementioned pharmaceutical forms are, as a rule, produced with the addition of bulking agents, binders, disintegrants, lubricants or other ancilliary substances. Bulking agents and dry binders used for tablets are, inter alia, lactose, sucrose, mannitol, sorbitol, microcrystalline cellulose, starch, dicalciumphosphate and polyglycols. Examples of binders suitable for granulation are starch, alginates, polyvinylpyrrolidone and carboxymethyl cellulose. Examples of suitable flow regulators are starch, talc and silicon dioxide. Lubricants which can be used in the mechanical production of tablets are magnesium stearate and other metal soaps. Conventional tablet disintegrants include starch, cellulose derivatives and crosslinked polyvinylpyrrolidone.
Depending on the application and the active substance, the copolymers according to the invention are advantageously used in neutralized, partly neutralized or unneutralized form. If the copolymers are in unneutralized form, it is often advantageous for a base or a proton acceptor, consisting either of another ancillary substance and/or directly of the active substance, to be present.
If the active substance is basic, it can be wholly or partly in salt form with the copolymer according to the invention.
The copolymers are prepared by processes disclosed in the literature, such as solvent polymerization, suspension polymerization or emulsion polymerization, with emulsion polymerization being preferred.
The emulsion polymerization is carried out in a conventional way using initiators such as peroxo or azo compounds, for example dibenzoyl oxide, t-butyl perpivalate, t-butyl per-2-ethylhexanoate, di-t-butyl peroxide, t-butyl hydroperoxide, alkali metal or ammonium persulfates, azobisisobutyronitrile, 2,2xe2x80x2-azo-bis (2-methylbutyronitrile), 2,2xe2x80x2-azobis(2,4-dimethylvalero-nitrile), 1,1xe2x80x2-azobis(1-cyclohexanecarbonitrile), 2,2xe2x80x2-azo-bis (2-amidinopropane)salts, 4,4xe2x80x2-azobis(4-cyanovaleric acid) or 2-(carbamoylazo)isobutyronitrile etc., hydrogen peroxide or redox initiators. The initiators are normally employed in amounts of up to 10, preferably 0.02 to 5, % of the weight of monomers to be polymerized.
The polymerization is carried out in the presence of an emulsifier and/or protective colloid conventional for these purposes. Examples of suitable protective colloids are polyvinyl alcohols, cellulose derivatives or polyvinylpyrrolidones. The emulsifiers can be anionic, cationic or nonionic in nature. Examples of suitable emulsifiers are ethoxylated mono-, di- and trialkylphenols, ethoxylated fatty alcohols or sorbitan esters, alkali metal and ammonium salts of alkyl sulfates or alkyl ether sulfates, of alkylsulfonic acids, of ligninsulfonic acid and of alkylarylsulfonic acids or alkyldiphenyl oxide sulfonates.
The emulsion polymerization normally takes place with exclusion of oxygen at from 20 to 200xc2x0 C. The polymerization can be carried out batchwise or continuously.
It is preferable to meter at least part of the monomers, initiators and, where appropriate, regulators such as aldehydes, halogen compounds or sulfur compounds, for example formaldehyde, acetaldehyde, bromotrichloromethane, mercaptoethanol, thioglycolic acid or dodecyl mercaptan, at a constant rate into the reaction vessel during the polymerization. The monomers and the initiator can, however, also be initially present and polymerized in the reactor, in which case cooling is necessary where appropriate.
This results in copolymers with a weight average molecular weight of from 50,000 to 2 million. Copolymers with an average molecular eight of from 20,000 to 1,500,000, in particular 120,000 to 400,000, are particularly suitable for their use according to the invention.
Suitable for drying the polymer dispersion are all conventional technologies such as thin-film drying, fluidized bed drying, spray drying or freeze drying.